Two stroke engines



May 3, 1960 A. BRUEDER 7 2,935,053

TWO STROKE ENGINES Filed Nov. 27, 1956 2 Sheets-Sheet l A 0/0/08 BruederBy his of/omeys May 3, 1960 A. BRUEDER 2,935,053

TWO STROKE ENGINES Filed Nov. 27, 1956 2 Sheets-Sheet 2 ANTOINE BRL EDERmuxm Ins afforne'vs 2,935,053 a TWO STROKE ENGINES Antoine Brueder,Paris, France, assignor to Societe Anonyme Andre Citroen, Paris, France,a French company In a four-stroke engine all of the air enteringthe-engine is usable for combustion. As a result the rate of fueldelivery will automatically have the correct value provided the rate offuel delivery is made proportional to the rate of air delivery. Inparticular the fuel may be metered in response to the rate of airdelivery as measured by the degree of suction generated at the neck of aventuri nozzle; this is the procedure used in carburettors and in sometypes of mechanical metering devices.

In a two-stroke engine on the other hand part of the air flows throughthe engine during the scavenging period and is lost insofar ascombustion is concerned. This fraction will be large in proportion asthe power output of the engine is large; for it is well-known that thepower output of a two-stroke engine may be varied by correspondinglyvarying the scavenging air ratio, i.e. the ratio of the rate of volumeflow of air delivered, to the volume generated per unit time by thepistons of the engine. Where the fuel supply means are operatedindependently from the air supply means, as by injection, then the fuel.supply rate must be made proportional to the rate of supply of the airactually used for combustion rather than to the rate of supply ofscavenging air.

In some types of two stroke fuel injection engines, the fuel rate isregulated in response to the suction obtaining at the neck of a venturiinterposed in the air supply circuit, the suction acting on thediaphragm or piston of a flow regulating device. Such apparatus are opento the above indicated drawback. For, assuming that the supply rate hasthe proper value for operation at the maximum scavenging air ratio, theratio of the air supply rate usable for combustion to the scavenging airsupply rate will increase as the scavenging air ratio decreases; theflow regulator will then not deliver sufiicient amounts of fuel.

It is an object of the present invention so to improve two-strokeinjection engines that a correct fuel delivery rate will be maintainedregardless of the scavenging air ratio, and hence of the power output ofthe engine.

According to this invention the engine comprises means for regulatingthe rate of fuel delivery as a function of the pressure drop across anorifice through which the combustion gases are made to flow.

The orifice may be inserted in the exhaust pipe. Alternatively theexhaust port may be used as the orifice of the invention, the fueldelivery 'being controlled as a function of the scavenging air pressure;this is because the scavenging air pressure depends primarily on thepressure drop across the exhaust port.

According to the invention therefore the engine is utilized as a meansof flow measurement rather than using a venturi as in the type of engineabove indicated. Since the two-stroke engine behaves as an orifice ofpredetermined flow section, it might appear at first glance that theresult is identical in both cases. Actually, as the scavenging'air ratioincreases, the mean temperature of the gases flowing through the enginedecreases since the relative amount of air which passes into the exhaustduring F 2,935,053- Ice Patented M y 5 p the scavenging periodincreases; as a result the scavenging air pressure rises, but it does soless rapidly than it would if the temperature were to remain constant.Consequently, if the rate of fuel delivery is made to be a function ofthe scavenging air pressure, such fuel-feed rate will increase with thescavenging air ratio, but it will increase less swiftly than does thetotal air delivery rate; in fact it remains substantially proportionalto the combustion air delivery rate so that it automatically assumes thecorrect value.

Since it is the temperature of the gas flow through the engine whichacts to alter the scavenging air ratio, it will alternatively bepossible in order to measure the delivery rate, to utilize the pressuredrop through a venturi or a diaphragm inserted in the exhaust pipe asalready indicated above. It is simpler however to use the scavenging airpressure. v In the drawings:

Fig. 1 is a diagrammatic the invention.

Fig. 2 is a diagrammatic view of another embodiment.

As shown in the drawing the engine includes two cylinview of oneembodiment of ders 1 each formed with two intake ports connected withintake conduits 2 connected with a common manifold 3, and an exhaustport connected with the exhaust pipe 4.

Fitted in each of the conduits 2 is a butterfly valve 5, whichvalvesprovide for regulation of the scavenging air ratio.

The intake manifold 3 is connected with a compressor 6 which suppliesthe scavenging air and is bypassed by a check valve 7 serving to preventthe compressor discharge pressure from rising excessively when thevalves 5 ar moved to closed condition.

The injection nozzles 8 are supplied through a distributor valve 9 theoperation of which is synchronized with that of the engine and ametering regulator 10 connected with the distributor by a pipe 11. Thefuel passes from the supply pump to the regulator over a conduit 12 andthe excess thereof is returned to the pump by way of conduit 13. Theregulator 10 is controlled through a pipe 26 in response to thescavenging air pressure which is related and responsive to the pressuredrop in the combustion gases from the engine and is picked off at 14beyond the valves 5 and ahead of the cylinder 1.

The distributor valve 9 may comprise a housing in which revolves arotary valve disc 15 which has an axial passage communicating throughthe housing with the fuel pipe 11. The axial passage 17 which passesonly half Way through the valve disc 15 communicates with a radialpassage 18 which communicates with one or the other of the fuel pipesfor delivering the fuel to the cylinders 1. The valve disc 15 is mountedfixedly upon a shaft 16 which rotates with the motor.

The fuel regulator 10 may comprise a housing having pistons 21 and 22 inopposite ends sliding in cylindrical chambers. The pistons 21 and 22 arejoined together by a piston rod 23. In the face of the piston 22 is anatomizing orifice 24. Fuel entering through pipe 12 into the upper partof the chamber in which the piston 22 works and above the piston passesthrough the atomizer 24 and into the pipe 11 leading from the oppositeor lower end of said chamber to the distributor.

The piston 22 is responsive. to a reduction in the amount of fueldelivered. In the wall of the chamber about around that wall from theinlet 12 is an orifice communicating with the fuel return pipe 13. Asthe piston 22, is displayed, it varies the section of thi orifice whichis uncovered, in consequence of which the quantity of fuel returning tothe pump by the pipe 13 is varied. The pressure exerted on the piston 22is maintained in equilibrium with the pressure change or drop in thepiston 21. Hence, any change in pressure applied to the cover or uncovermore or less of the orifice leading to the fuel return pipe 13. As aresult, the amount of fuel fed through .the'atornizer 24 will varyi t at igln the-form illustrated. in Figure 2; which is claimed .in mycopending divisional application Serial No. 850,653, .filed. November 3,1959., 'andientitled Two Stroke Engines, acalibrated orifice 25 isplaced'in the exhaust pipe. The change in pressure created by the sizeof this orifice is-refiected upon the piston 21 by a pipe connecting theexhaust pipe 4 with the chamber in which the piston 21 works.

It will be understood that the invention is not limited to theembodiment described and illustrated but may cover modifications.

What I claim is:

In'a two-cycle internal combustion engine, a cylinder with intake andexhaust ports therein, air supply means connected with said intakeport-and an exhaust conduit connected with said exhaust port, fuelinjection means for delivering fuel into said cylinder and means forignitpiston 21 willchange the position of the piston 22 in" accordancewith movement of the piston 21 and will.

v T' I? 4: I i V ing said fuel, valve means in said' air supply meansfor regulating the air supply, pressure responsive means connected to apoint in the air. supply means between said intake port and said valvemeans and responsive to variations in the pressure thereat, andregulating means connected with said pressure responsive means and withsaid injection means for varying "the fuel delivery rate of said,injection means in proportion to said, pressure and independent of theengine speed.

keferencesCited the file of patent UNITED STATES PATENTS 2,012,998Junkers septa, 1935 2,078,934 Dillstrom May 4, 1937 2,244,669 BeckerJune 10, 1941 2,245,562 Becker June 17, 1941 2,260,688 Lllrange Oct. 28,1941 '2,383,979 Ly sh0lm Sept. 4, 1945 t FOREIGNPATENTS 722,388 GreatBritain Jan. 26, 1955

